Sand dune movements and dust storms are common in Arabian Gulf countries. It occurs because of the existence of fine particles on the surface of the top soils, which are poorly bonded and susceptible to erosion by wind and rain. This invention pertains to binder compositions useful for binding particulate matter and sand dunes.
Soluble silicates have been used as binders for many years and in many applications. It is a white powder or colorless solution that is readily soluble in water, producing an alkaline solution. As this alkaline solution is neutralized, colloidal silica aggregates to form a gel. To control aggregation, gelation time, and gel performance, grouting systems were developed over the last 100 years. These systems include: (a) acid reactant (phosphoric acid, sodium hydrogen sulfate, sodium phosphate, carbon dioxide solution), (b) alkaline earth and aluminum salts (calcium chloride, magnesium sulfate, magnesium chloride, aluminum sulfate), (c) organic compounds (glyoxal, acetic ester, ethylene carbonate formamide).
U.S. Pat. No. 1,827,238 to Joosten describes a process for solidifying permeable rock, loosely spread masses, etc. in which silicic acid is introduced into the mass followed by the introduction of carbon dioxide thus integrating and solidifying the treated mass.
U.S. Pat. No. 2,968,572 to Peeler, Jr. teaches a process of soil treatment in which the soil is contacted with a single liquid mixture comprising an aqueous alkali metal silicate, and amide, such as formamide and a metal salt such as sodium aluminate thereby forming a water-insoluble gel.
U.S. Pat. No. 4,043,830 to Suzuki discloses a process for consolidation of poor quality soil by injecting hardeners comprising, for example, a mixture of water and a gelling agent and a water glass aqueous solution containing a gelling agent such as ethylene glycol diacetate.
U.S. Pat. No. 4,056,937 to Suzuki teaches a soil consolidation process in which a hardener comprising an aqueous solution of water glass and an acidic reactant, such as phosphoric acid, is injected into the soil thereby solidifying the treated soil.
U.S. Pat. No. 4,416,694 to Stevenson et al. discloses foundry sand compositions made from foundry sand, an aqueous sodium silicate binder and an alkylene carbonate which are used to form molds and/or cores in metal casting.
U.S. Pat. No. 4,642,196 to Yah teaches a method and composition for controlling dust occurring in the production, handling, transport and storing of coal which includes applying such as by spraying an aqueous solution of a gelatinized starch.
U.S. Pat. No. 4,983,218 to Mascioli discloses a composition and method for hardening an alkali metal silicate solution using blends of alkylenediols, polyoxyalkylene glycols or hydroxyalkyl ethers. The hardened alkali metal silicate compositions are useful as binders in the preparation of foundry molds or in other applications requiring agglomeration of particulate matter.
U.S. Pat. No. 5,059,247 to Crawford et al. teaches a foundry sand composition that is self-hardening after a working life of about 10-20 minutes composed of foundry sand, a sodium silicate binder and a specifically defined polyester polycarbonate hardener.
U.S. Pat. No. 5,336,315 to Cuscurida et al. describes a process for soil stabilization in which soil particles are treated with an aqueous solution of an alkali metal silicate, and a carbonate reactant or gelling agent selected from the group consisting of an alkylene carbonate, such as ethylene carbonate, a polyester polycarbonate and mixtures thereof.
However, problems such as homogeneity, volume changes, loss of strength, and in-situ application still exist. Therefore, it is the purpose of this invention to provide a method to form a nano-sized dispersed structure comprising or consisting of aqueous sodium silicate solution and polyvinyl pyrrolidone (PVP) which controls aggregation and homogeneity, and a binder consisting of a nano-dispersed structure and calcium chloride dihydrate solution which controls system aggregation, homogeneity, gelling time, gel performance, and strength development. The invention also provides a method to immobilize sand dunes and wind-blown dust by using the binder.
Nano-sized composites consisting of aqueous sodium silicate solution and PVP, and reactant consisting of calcium chloride dihydrate solution can be injected as separate solutions, or can be premixed to form a single solution that is then injected. Treatment of soft soils by deep mixing with binders is the most frequently used method of ground improvement and is increasingly being used internationally over the last decades. Success of any treatment method is directly related to overall strength development which is a direct function of binder composition, method of application, substrate formation and composition in terms of particle-size distribution, grain size, particle shape and moisture content, the ability of the grout to adhere to particle surfaces, and curing environment.